1. Field of the Invention
The present invention relates to a member mounting structure and particularly relates to an improvement of a mounting structure, which with positioning a second member by a boss disposed on a first member, fixes a second member to the first member integrally by a mounting screw.
2. Description of the Prior Art
A mounting structure is known which presses a second member against a first member and integrally fixes it thereto. That is, in a state where a predetermined second member is positioned relative to a first member having a tubular boss with a screw fastening hole at its center using the boss as a reference, a mounting screw is screwed into the screw fastening hole. Thus, the second member is pressed against the first member and is thereby fixed integrally thereto by a head of the mounting screw.
A parts mounting apparatus disclosed in Patent Document 1 (Japanese Published Utility Model Application No. H 02-44106) is an example of such a structure. As shown in FIG. 5, a clock 102 is mounted integrally as a second member to a center cluster 10 which is an interior part for a vehicle as a first member. FIG. 5A is a longitudinal sectional view of mounting portions, and FIG. 5B is a perspective view of a supporting portion 120 as viewed from side of a positioning tube portion 124.
In FIG. 5, on a rear surface (upper surface in FIG. 5A) of the center cluster 100, a boss 106 of cylindrical shape having a screw fastening hole 108 at its center is protruded integrally at a periphery of a window hole 104. Four reinforcing ribs 110 are disposed radially on an outer peripheral surface of the boss 106. Meanwhile, the clock 102 has a supporting portion 120 in correspondence to the boss 106, on which a penetrating hole 122 is formed in correspondence to the screw fastening hole 108. At a circumference of the penetrating hole 122, a cylindrical positioning tubular portion 124 to be fitted to an outer peripheral side, that is fitted radially outward of the boss 106 protruding toward the center cluster 100, is provided. The positioning tubular portion 124 has four slits 126 provided for avoiding interference with the reinforcing ribs 110.
The clock 102 is positioned relative to the center cluster 100 so that the positioning tubular portion 124 is fitted to the outer peripheral side i.e. outer peripheral surface of the boss 106. In this state, a tapping screw 128 is screwed into the screw fastening hole 108 through the penetrating hole 122. The tapping screw 128 is thereby screwed to the screw fastening hole 108 while tapping an internal thread thereon, so that a head of the tapping screw 128 presses the supporting portion 120 against a tip surface of the boss 106 and thereby fixes it thereto integrally. Here, because the cylindrical boss 106 and the positioning tubular portion 124 are mutually fitted over a predetermined length, the positioning of the clock 102 is maintained satisfactorily, so that a fastening work by the tapping screw 128 can be performed readily.
FIG. 6 is a sectional view showing another conventional example. On a first member 130 which is a vehicle interior part, etc., a cylindrical boss 134 having a threaded hole 132 as a screw fastening hole at its center and protruding integrally is provided. On an outer peripheral surface of the boss 134, a plurality of reinforcing ribs 136 are disposed radially except for a predetermined axial length at a tip portion of the boss 134.
Meanwhile, a second member 140 is provided with a positioning hole 142 fitted to the outer peripheral side of the boss 134 to be positioned. The second member 140 has a thickness which is greater than the protruding dimension of the boss 134 from the reinforcing ribs 136. With the boss 134 fitted in the positioning hole 142 and the second member 140 contacted with reinforcing ribs 136, a mounting screw 144 is screwed into the threaded hole 132 of the boss 134. In this way, a head of the mounting screw 144 presses the second member 140 against the reinforcing ribs 136 to fix it integrally to the first member 130.
However, in the mounting structure of FIG. 5, because the boss 106 and the positioning tube portion 124 which are to be fitted mutually are disposed in a confronting manner, they must be positionally aligned in a mutually separated state before fitted together. This aligning process is troublesome, which hinders a good mounting workability and makes an automation of the mounting work difficult.
Also, unless the slits 126 formed in the positioning tube portion 124 and the reinforcing ribs 110 are aligned in positions thereof, the boss 106 and the positioning tube portion 124 cannot be fitted together. This also worsens an aligning workability as well.
Meanwhile, in the mounting structure of FIG. 6, the second member 140 is provided with the positioning hole 142. By adjusting position of the second member 140 with slidable-contacting with the tip end of the boss 134, the positioning hole 142 can be fitted readily to the boss 134. However, because the fitting length is less than thickness of the second member 140, there is a fear that the second member 140 may be detached or disengaged readily. In order to prevent such detachment, the fastening work of the mounting screw 144 must be performed while pressing the second member 140, which results in poor mounting workability. In this case, to improve the mounting workability, a positioning boss and a positioning hole must be provided additionally. Also, when the mounting screw 144 is fastened while the second member 140 rides on the boss 143, defective mounting structure is produced to worsen a yield.